1. Field of the Invention
This invention relates to a storage device for storage of optional data and the area management information for supervising the state of the area in which to store the data, a data processing system and a data processing method employing this storage device.
2. Description of the Related Art
Up to now, a card type external storage device, referred to hereinafter as a memory card, employing a flash memory (electrically erasable programmable read-only memory (ROM)) as a recording medium, has been proposed as an external data storage device used for an electronic equipment.
In this memory card, optional data and the management information as ancillary data are stored in a memory as a storage medium. When these data and the management information are sent from the memory card to e.g., a host side computer, the data or the management information is corrected for errors, using the error correction codes, to correct the data for errors produced by cell malfunctions, before outputting the data or information.
As the above management information, the information for management of the state of an area for data storage (area management information), such as the information specifying whether or not the area holding the data on memory is usable, is occasionally stored, in addition tor the data-dependent information for supervising the data (data management information), such as logical addresses indicating the sequence of the stored data.
Since the area management information is the information concerning an in-memory area, that is information independent of data, there may arise the necessity of rewriting the information after storage of the data, and hence the area management information is usually adapted to be rewritten by itself without rewriting the data.
Also, if an error is produced in the area management information, and a usual error correction code is used to correct the information for errors, the error correction codes need to be rewritten every time the information is rewritten. Thus, for the area management information, the same information is desirably distributed in plural bits and stored in this state in order to combat errors without employing the error correction code for error correction.
Meanwhile, if the same information is distributed in plural bits and stored in this state to combat errors, the area management information occasionally cannot be corrected for errors on occurrence of malfunctions in plural cells in which the same information is stored. It is therefore desirable that the area management information once corrected for errors can be discriminated to be the information corrected for errors, so that, in case of storage in the memory card next time, the data will be stored in an area other than the area subjected to the malfunction.